I'm past level 5, but I haven't done a gym yet, because I'm still deciding on a team to join.
While I like Team Mystic the most (because of it's name, leader, color, and mascot Pokemon, I don't want to join the most popular team. So I was going to pick Team Instinct, and then I found out my three sisters were joining that team, and thought it'd be more fun to beat them in all the gyms in the area, rather than join their team. xD And I'm really just not a fan of Valor, so I have no idea what to pick yet xD